The influence of protein and calorie malnutrition during pregnancy followed by full feeding to day 15 retards the maturation of the hypothalamo-hypophyseal-adrenal axis as indicated by a subnormal response to either stress. Plasma and adrenal corticosterone are measured and refeeding will be extended to 20 and 25 days to further assess the maturational delay. The fetal corticosterone environment will also be assessed in the malnurished mother. Limiting calorie intake during lactation only enhances adrenal axis sensitivity at 15 and 20 days and will be studied for an effect of 10% casein and for dexamethosone blocking. The influence of malnutrition during pregnancy or lactation on the development of circadian corticosterone rhythms will be studied as well as the influence of thyroid hormone in modifying the effects of malnutrition. BIBLIOGRAPHIC REFERENCES: Chan, S.W.C. and J.H. Leathem, 1977. Placental steroidogenesis in the rat: Comparision of the normal and giant placentae. Endocrinology, in press. Chan, S.W.C., J.H. Leathem and T. Esashi, 1977. Testicular metabolism, serum testosterone and its response to human chorionic gonadotropin in aging male rats. Endocrinology, in press.